There is a critical need to be able to model human organ systems, such as the kidney, to improve our understanding of drug efficacy, safety, and toxicity, especially during drug development. The kidneys in general and the proximal tubule specifically, play a central role in the elimination of xenobiotics. With recent advances in molecular investigation, considerable information has been gathered regarding the substrate profiles of the individual transporters expressed in the proximal tubule. However, we have little knowledge of how these transporters coupled with intracellular enzymes and influenced by metabolic pathways form an efficient secretory and reabsorptive mechanism in the renal tubule. Moreover, while kidney disease is a public health problem that affects more than 27 million people in the US adult population, little is understood about the impact of kidney disease on drug disposition. The goal of this application is to develop a model system that predicts drug excretion by the human kidney, emulating healthy and disease related conditions. We propose to robustly model the human kidney utilizing an in vitro 3-dimensional modular microphysiological system with human kidney-derived cells. The microphysiological system will accurately reflect human physiology, be usable to predict renal handling of xenobiotics, and will assess response to kidney injury from endogenous and exogenous intoxicants. We also propose to work closely with other investigators in order to ultimately link our kidney module with other organ or tissue modules to achieve a 'systems biology and medicine' approach in the UH3 phase. To achieve this goal, we have established a multidisciplinary investigative team with expertise in kidney based cellular and molecular biology, renal toxicology, pharmacokinetic modeling, vascular biology, and biomedical engineering. This will create a unique resource of great utility for the UH2/UH3 Consortium. The proposed research plan, by improving our understanding of the determinants of xenobiotic excretion by modeling kidney cell function in health and disease, has the potential to dramatically impact the public health.